[0001] Various method are used for producing a partially cross-linked rubber-resin composition
comprising a partially cross-linked peroxide-curable olefin copolymer rubber and a
polyolefin resin. As the olefin copolymer rubber, ethylene/propylene copolymer rubber
and ethylene/propylene/non-conjugated polyene copolymer rubber are typical.
[0002] One method disclosed in Japanese Unexamined Patent Publication No. 57-22036 (unpublished
at the priority date of the present application) comprises melting and kneading the
copolymer with an organic peroxide in a Banbury mixer to provide dynamic heat treatment
for partial cross-linking, followed by mixing with a polyolefin resin. Another method
disclosed in US-A-3806558 and US-A-4197381 comprises melting and kneading the copolymer
rubber with an organic peroxide in a Banbury mixer in the presence of a peroxide-decomposing
polyolefin resin such as polypropylene. Both of these are batchwise processes and
so are not very economical methods of production. Further, in the former it is difficult
to obtain a product of constant quality because of insufficient mixing of the partially
cross-linked rubber and the polyolefin resin.
[0003] In order to obtain a homogeneous product of constant quality it is preferable to
preliminarily melt and mix the copolymer rubber and a peroxide-decomposing polyolefin
resin such as polypropylene and to form particles from the blend, and then to melt
and knead the particles with an organic peroxide in an extruder for the dynamic heat
treatment, for example, as described in US-A-4212787. This method incurs the disadvantages
of requiring the preliminary step of melting and mixing the copolymer rubber and the
polyolefin resin.
[0004] It would therefore be desirable to provide a continuous, single step, economic and
advantageous method of producing a homogeneous partially cross-linked rubber-resin
composition.
[0005] In the invention a partially cross-linked rubber-resin composition is made by melting
and mixing a peroxide-curable olefin copolymer rubber and a peroxide-decomposing polyolefin
resin with an organic peroxide compound, the rubber and the resin being subjected
to dynamic heat treatment in the presence of the peroxide, and the method is characterised
in that the rubber, in particulate form, the resin and the peroxide are fed to a twin
screw extruder in which the dynamic heat treatment is carried out, under the condition:
wherein "x" stands for weight of the copolymer rubber (g/100 particle), and "y" stands
for specific energy at the extrusion (kWhr/kg).
[0006] Thus, in the invention particulate rubber, resin and peroxide are fed directly to
the twin screw extruder and it is possible by this method to produce a homogeneously
mixed partially cross-linked copolymer rubber-resin composition having good properties.
We find that the size of the rubber particles fed into the extruder significantly
influences the properties of the final composition. Also the mechanical energy given
by the twin screw extruder to the materials fed into it influences the dispersiblity
of the partially cross-linked copolymer rubber and the polyolefin resin. The specific
energy, which is correlated to the size of the copolymer rubber particles, preferably
exceeds a certain level for the purpose of obtaining homogeneous mixing and optimum
properties of the final product, as is described in more detail below.
[0007] We found that the use of a conventional single screw extruder was much less satisfactory.
Although it is possible to choose the operating conditions of the single screw extruder
so as to provide sufficient specific energy to the materials it is in practice almost
impossible to achieve satisfactory dispersion of the partially cross-linked copolymer
rubber and resin. As a result it is difficult or impossible to obtain, using a single
screw extruder, the desired products having good properties.
[0008] The peroxide-curable olefin copolymer rubber to be partially cross-linked may be
an essentially amorphous, elastic copolymer mainly composed of olefins, such as ethylene/propylene
copolymer rubber, ethylene/propylene/non-conjugated diene terpolymer rubber, ethylene/butene
copolymer, ethylene/1-butene/non-conjugated diene terpolymer rubber and ethylene/butadiene
copolymer rubber. The elastic copolymer may be cross-linked when mixed with an organic
peroxide and kneaded under heating to form a rubber of less or little fluidity. The
copolymer rubber is made by copolymerizing ethylene and the alpha-olefin of 1 to 12
carbon atoms (e.g. propylene, butene-1, pentene-1, hexene-1, 4-methyl-1-pentene and
5-methyl-1-hexene) in a molar ratio of preferably about 50/50 to 95/5, more preferably,
about 55/45 to 85/15. In cases when a non-conjugated polyene such as dicyclopentadiene,
1,4-hexadiene, cycloctadiene, vinyl norbornene, methylene norbornene or 5-ethylidene-2-norbornene
is copolymerised, it is preferable that the amount of polyene is such that the iodine
value is not more than about 50, preferably about 40 or less. Preferable the Mooney
viscosity ML,
14 (100°C) of the copolymer rubber is about 10 to 100, particularly about 40 to 150.
[0009] As the peroxide-decomposing polyolefin resin, the following resins may be used: crystalline
polypropylene-based resins such as homopolymers of propylene and copolymers of at
least 85 molar% propylene with' an alpha-olefin having 2 to 10 carbon atoms other
than propylene, crystalline poly(1-butene)-based resins such as homopolymers of 1-butene,
and copolymers of at least 85 molar% 1-butene with an alpha-olefin having 2 to 10
carbon atoms other than 1-butene and poly(4-methyl-1-pentene)-based resins such as
homopolymers of 4-methyl-1-pentene, and copolymers at least 85 molar% 4-methyl-1-pentene
with an alpha-olefin having 2 to 10 carbon atoms other than 4-methyl-1-pentene. The
polypropylene-based resins and poly(1-butene)-based resins are preferable. Particularly,
polypropylene-based resins having a melt index (230°C) of about 0.1 to 100, especially
about 0.5 to 50 are very useful.
[0010] The peroxide-curable olefin copolymer rubber and the peroxide-decomposing polyolefin
resin are mixed in a weight ratio of, generally about 10/90 to 95/5, preferably about
20/80 to 90/10. If the amount of the copolymer rubber is less than the above lower
limit, excess decomposition of the resin component by the organic peroxide occurs
and causes insufficient cross-linking of the copolymer rubber component as well as
too much decrease in viscosity of the resin component, which results in poor dispersion
between the partially cross-linked rubber and the resin. On the other hand, if the
copolymer rubber is used in an amount higher than the above limit, the amount of resin
component in the product is so low that strength of the product is unsatisfactory.
Also, the resin component will have lower fluidity because the amount of the resin
having decreased molecular weight is small, and therefore it is difficult to obtain
a sufficient homogeneity in mixing, even if more of the resin component is added later
to the dynamically heat treated materials with the intention to improve strength of
the product.
[0011] Examples of the organic peroxide are: dicumyl peroxide, di-tert.-butyl peroxide,
2,5-dimethyl-2,5-di(tert.-butyl peroxy) hexane, 2,5-dimethyl-2,5-di-(tert.-butylperoxy)hexine-3,
1,3-bis(tert.-butyl peroxy isopropyl)benzene, 1,1-bis(tert.-butyiperoxy)-3,3,5-trimethy)
cyclohexane, n-butyl-4,4-bis(tert.- butylperoxy)valerate, benzoyl peroxide, p-chlorbenzoyl
peroxide, 2,4-dichlorbenzoyl peroxide, tert.-butyl peroxy benzoate, tert.-butyl peroxide
isopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert.-butyl cumyl peroxide.
[0012] Out of these organic peroxides, preferable compounds in view of the anti-scorch stability
and odour are 2,5-dimethyl-2,5-di(tert.-butyl peroxy)hexane, 2,5-dimethyl-2,5-di(tert.-butyl
peroxy)hexine-3, 1,3- bis(tert.-butyl peroxy isopropyl)benzene, 1,1-bis-(tert.-butyl
peroxy)-3,3,3-trimethyl cyclohexane, and n-butyl-4,4-bis(tert.-butyl peroxy)valerate.
Among them 1,3-bis(tert.-butyl peroxy isopropyl)benzene is the best.
[0013] The organic peroxide is used in an amount of about 0.01 to 1 % by weight, preferably
about 0.1 to 0.5% by weight, based on the total amount of the peroxide-curable olefin
copolymer rubber, peroxide-decomposing polyolefin resin and optional components mentioned
below.
[0014] The peroxide-curable olefin copolymer rubber is used in the form of particles. In
this specification, the term "particle" means any particle form including pellet,
granule, crumb and powder. Pellets are often preferred. The particles preferably have
a maximum dimension (for instance a longer diameter) "z" not exceeding 25 mm, preferably
0.5 to 20 mm. This condition can be usually satisfied with the particle having a weight
"x" not exceeding about 200 g/100 particles. It is preferable to use particulate copolymer
rubber weighing about 50 g/100 particle or less. On the other hand, very small particles
are difficult to produce and, even if commercially produced, expensive. So it is generally
advisable to use particles weighing about 0.1 g/100 particle or more, preferably about
1 g/100-particle or more. The copolymer rubber particle of such size can be easily
produced in accordance with the method, for example, described in U.S. Patent No.
3,586,089 using a pelletizer which performs removal of polymerization medium and pelletizing
simultaneously.
[0015] The other component, the polyolefin resin should be also in the form of particles.
Though the size of the resin particle may not be of the same fineness, it is generally
preferable that the weight is in the range of about 1 to 10 g/100-particle.
[0016] The dynamic heat treatment according to the present invention is carried out under
the condition of the specific energy fed to the twin screw extruder:
preferably, 1.5?y?0.003x+0.15, wherein the specific energy is defined as the quotient
given by dividing the difference of the driving power of the extruder in which the
dynamic heat treatment is performed (HP
1KW) and the driving power without load or no material feed under the same screw rotation
(HP
ZKW) with the extruding amount (Q kg/hr). The unit thereof is KWhr/kg.
[0017] The specific energy may be varied by changing the operation conditions of the extruder.
It may increase by increase in rotation of the screws, use of a finer screen pack,
or decrease in feeding amount of the materials. Also, it depends on the type of the
screws. Screws with shallower grooves will give increased specific energy.
[0018] Preferably the dynamic heat treatment gives the specific energy equal to or higher
than the energy of the above equation, which energy is determined by the size of the
rubber particle. A lower specific energy is unsatisfactory for the dispersion or thorough
mixing, and gives the partially cross-linked rubber-resin composition having inferior
properties. However, it is preferable that the specific energy does not exceed about
1.5 KWhr/kg, particularly about 1.0 KWhr/kg. If too much specific energy is given,
local elevation of temperature will occur due to transfromation of mechanical energy
to frictional energy, resulting in deterioration of properties of the product composition.
Such an excess energy is of course neither necessary nor economical.
[0019] Various types of twin screw extruders which may give the above described specific
energy may be used and the two screws may mutually engage or not. Examples of commercially
available machines are Werner Extruder (made by Werner in West Germany, two screws
engaging and rotating in the same direction). CIM-90 Extruder (made by Nippon Seiko,
two screws not engaging and rotating in the different directions) and BT-80 Extruder
(made by Hitachi, two screws engaging and rotating in the different directions).
[0020] The dynamic heat treatment using the twin screw extruder is carried out under the
conditions of the temperature at which the materials melt, generally about 200 to
280°C, preferably about 210 to 250°C, and the residence time is, generally about 15
to 240 seconds, preferably about 30 to 180 seconds.
[0021] Homogeneous and moderate cross-linking reaction can be expected if a cross-linking-aid
is present during the heat treatment. Such cross-linking aids are: sulphur, p-quinone
dioxime, p,p'-dibenzoyl quinone dioxime, N-methyl-N,4-dinitrosoaniline, nitrobenzene,
diphenyl guanidine, trimethylol propane-N,N'-m-phenylene dimaleimide, divinyl benzene,
triallyl cyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate,
trimethylol propane trimethacrylate, allyl methacrylate, vinyl butylate, and vinyl
stearate.
[0022] Out of the above compounds, divinyl benzene is the most preferable, because it is
easy to handle and gives the composition having well-balanced properties. More particularly,
divinyl benzene is liquid at a normal temperature and dissolves organic peroxide and
has good compatibility with the peroxide-curable copolymer rubber and the polypropylene
resin. It therefore is useful as a dispersing agent or diluent of the organic peroxide
to improve dispersibility of the organic peroxide into the components of the composition,
particularly into the peroxide-curable copolymer rubber component so as to cause homogeneous
and moderate cross-linking thereof. Also, divinyl benzene itself provides a radical
which acts as a chain transfer agent and cross-linking agent, and therefore, gives
cross-linking effect higher than that given by sole use of an organic peroxide cross-linking
agent. Further, divinyl benzene exhibits so good reactivity to the organic peroxide
that very few portion remains in the produced partially cross-linked rubber-resin
composition as the monomer, which may, if present, give odour to the product. Divinyl
benzene may be used in the form of a mixture with some other materials such as hydrocarbons.
[0023] The above mentioned various cross-linking aids are used in an amount of up to 2 parts
by weight, preferably about 0.3 to 1 parts, based on the total 100 parts by weight
of the peroxide-curable copolymer rubber and the peroxide-decomposing polyolefin resin
components. Too much addition of the cross-linking aid may, if a large amount of the
organic peroxide is used, accelerate the cross-linking, and as the result, the partially
cross-linked rubber-resin composition may have decreased homogeneity and low impact
strength. On the other hand, if the amount of the organic peroxide is small, the cross-linking
aid will remain in the partially cross-linked rubber-resin composition as unreacted
monomer, which causes undesirable change in properties because of thermal effect during
processing of the product.
[0024] For the purpose of improving further properties of the partially cross-linked rubber-resin
composition, mineral oil softener, peroxide-non-curable hydrocarbon rubber and peroxide-curable
polyolefin resin may be optionally added. Usual amount of addition is in the range
of 0 to 400 parts by-weight, preferably 5 to 300 parts by weight, based on total 100
parts by weight of the rubber-resin composition. These additives can be added at the
dynamic heat treatment. It is preferable to preliminarily add these additives to the
rubber and/or resin. The mineral oil softeners are useful for improving processability
of the partially cross-linked rubber-resin composition. The same effect can be obtained
by addition of the peroxide-non-curable hydrocarbon rubber such as polyisobutylene,
butyl rubber and propylene-ethylene copolymer rubber containing not higher than 50%
ethylene unit. The peroxide-curable polyolefin resin such as polyethylene improves
strength and impact resistance of the partially cross-linked rubber-resin composition.
[0025] As described above, it is possible to produce partially cross-linked rubber-resin
compositions, which are homogeneously blended and have good properties, economically
in single step by dynamic heat treatment in a twin screw extruder under specific conditions
in accordance with the present invention. The obtained partially cross-linked rubber-resin
compositions may be used as they are or as mixtures with further peroxide-curable
or peroxide-decomposing polyolefin resin. Those compositions containing relatively
large amount of the partially cross-linked rubber component are useful as thermoplastic
elastomers, and those compositions containing relatively large amount of the polyolefin
resin are useful as polyolefin resin composition having improved impact strength.
[0026] The present invention will be further illustrated by the following. examples.
Materials used
[0027]
EPT-1: 100 parts by weight of ethylene/propylene/dicyclopentadiene terpolymer rubber
[molar ratio of ethylene/propyiene:78122, ML, 14 (100°C):160, iodine value:13L to which 40 parts by weight of mineral oil softener
[PW-100, made by Idemitsu Petrochemical] is added.
EPT-2: ethylene/propylene/ethylidene norbornene terpolymer rubber [molar ratio of
ethylene/ propylene:79/21, ML,,4 (100°C):100, iodine value:15]
PP-1: crystalline polypropylene having melt index (230°C) of 12 (weight of the particle:3
g/100- particle)
PP-2: crystalline polypropylene containing a small quantity of copolymerised ethylene
having melt index (230°C) of 30 (weight of the particle:3 g/100-particle)
PER: propylene/ethylene copolymer rubber [molar ratio of propylene/ethylene: 70/30,
[η] (135°C, decaline):3.0 dl/g, weight of the particle:3 g/100-particle]
[0028] Organic Peroxide: 1,3-bis(tert.-butyl peroxyisopropyl) benzene
Procedures
[0029] Particles of EPT-1, PP-1 or PP-2, and PER and/or mineral oil softener for the low
hardness series, were preliminarily blended in a Henshel Mixer for 60 seconds, and
the blends of certain amounts were fed to various extruders through constant feeders.
Samples were taken by strand-cutting at dies of the extruders.
[0030] In the Controls (shown in Tables I and II), conventional single screw extruder of
dia.-90 mm (P-90, made by Nippon Seiko) was used, with which two kinds of screws,
i.e. a full freight screw for pelletizing and an end-damaged screw having a seal ring
for resin-blending (UD=28 in both the screws) were tested. Detailed operation conditions
were as follows:
[0031] In some examples and the Controls for comparison therewith (shown in Tables III through
VII), twin screw extruder (W & P, made by Werner, diameter 90 mm, UD=43) was used.
The specific energy was varied by changing the screw rotation and the extrusion rate.
Detailed operation conditions were as follows:
[0032] In the other examples and the Controls for comparison therewith (shown in Tables
VIII and IX), a twin screw extruder (made by Hitachi, diameter 80 mm, L/D=16) was
used. The specific energy was varied by changing the screw rotation and the extrusion
rate. Detailed operation conditions were as follows:
Evaluation
1. Homogeneity:
[0033] The extruded particles were press-formed at 200°C to form thin sheets of thickness
0.2 to 0.4 mm, and the surfaces thereof were inspected.
(Grades) A: quite homogeneous
B: a certain extent of abnormality
C: serious abnormality
2. Processability:
1) Processability at Injection Moulding
[0034]
Machine: Dynamelter (made by Meiki Manufacturing)
Temperature: 200°C
Pressure of Injection: primary 1300 kg/cm2
secondary 700 kg/cm2
Injecting Pressure: maximum
Processing speed: 90 seconds/cycle
Mould: square plates type with two point gates
Product: three types of square plates (length: 300 mm, width: 180 mm, and thickness:
2, 4 and 7 mm) The surfaces of the product plates were inspected as done for the above
sheets.
2) Processability at Extrusion Moulding
[0035]
Machine: 40 mm-diameter extruder (made by Toshiba Machinery)
Temperature: 210°C
Die: straight die (die/core=12.5 mm/10.0 mm)
Drawing Speed: 10 m/min.
Product: tube
[0036] The surfaces of the product tubes thus obtained were inspected as done for the above
sheets.
3. Basic Properties
[0037] The above injection-moulded square plates (thickness 2 mm) were subjected to measurement
of stress at 100% elongation, stress and elongation at breaking, surface hardness
and permanent strain (at 100% elongation) in accordance with the testing method defined
by JIS K-6301.
[0038] Notes on the Results shown in Tables I through XI.
Table I:
[0039] A single-screw extruder was used, and the specific energy was varied in the range
from 0.12 to 0.45 by changing rotation of screw and feeding rate. The obtained products
of high hardness series were not satisfactory because of insufficient homogeneity
and some other properties. The extruder used in this Table (and in Table II) was either
Type 1 or Type 2. Type 1 is a full freight extruder and Type 2 was end-damaged with
seal ring.
Table II:
[0040] Another single-screw extruder was used, and the specific energy was varied in the
range from 0.11 to 0.41 by changing rotation of screw and feeding rate. The obtained
products of low hardness series were also not satisfactory because of insufficient
homogeneity and some other properties.
Table III to VII:
[0041] The twin screw extruder made by Werner was used, and the specific energy was varied
by changing rotation of screw and extrusion rate. From the experimental data, it was
found that the factors giving satisfactory products are as follows:
[0042] Thus, it was concluded that the specific energy "y" should be such a value as determined
by the weight of the copolymer rubber particle "x" according to the equation below:
[0043]
preferably
[0044]
Table VIII to IX:
[0045] A twin screw extruder made by Hitachi was used, and the specific energy was varied
by changing rotation of screw and extrusion rate. The data showed that the factors
giving satisfactory products are as follows:
Table X:
[0046] A twin screw extruder made by Hitachi was used to prepare the Low Hardness Series-2.
The specific energy was varied by changing rotation of screw and extrusion rate.
1. Verfahren zur Herstellung einer teilweise vernetzten Kautschuk-Harz-Zusammensetzung
durch Schmelzen und Mischen eines Peroxid-härtbaren Olefincopolymer-Kautschuks und
eines Peroxidzersetzenden Polyolefinharzes mit einer organischen Peroxidverbindung,
wobei bei dem Verfahren der Kautschuk und das Harz in einem Gewichtsverhältnis im
Bereich von 10:90 bis 95:5 gemischt werden und einer dynamischen Wärmebehandlung in
Anwesenheit des Peroxids unterworfen werden, dadurch gekennzeichnet, daß der teilchenförmige
Kautschuk und das Harz und Peroxid in eine Doppel schnecken-Strangpresse gegeben werden,
in welcher die dynamische Wärmebehandlung durchgeführt wird, und zwar unter der Bedingung:
worin "x" das Gewicht des Copolymer-Kautschuks (g/100 Teilchen) darstellt und "y"
die spezifische Energie beim Strangpressen (kWhr/kg) ist.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Kautschukteilchen eine
maximale Dimension von nicht mehr als 25 mm haben.
3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß die Kautschukteilchen eine
maximale Dimension von 0,5 bis 20 mm haben.
4. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß x=1 bis 50 ist.
5. Verfahren nach Anspruch 3 oder 4, dadurch gekennzeichnet, daß y=1.5 oder weniger
ist.
6. Verfahren nach einem der vorausgehenden Ansprüche, dadurch gekennzeichnet, daß
das Polyolefin-Harz in die Strangpresse in Teilchenform mit einem Gewicht im Bereich
von 1-10 g/100 Teilchen gegeben wird.
7. Verfahren nach einem der vorausgehenden Ansprüche, dadurch gekennzeichnet, daß
das Gewichtsverhältnis Kautschuk:Harz=20:80 bis 90:10 ist.
8. Verfahren nach einem der vorausgehenden Ansprüche, dadurch gekennzeichnet, daß
ein Vernetzungs-Hilfsmittel, vorzugsweise Divinylbenzol, während der Wärmebehandlung
anwesend ist.
9. Verfahren nach einem der vorausgehenden Ansprüche, dadurch gekennzeichnet, daß
der Kautschuk ein amorphes Olefincopolymer oder ein amorphes Copolymer von Olefinen
und einem nicht-konjugierten Dien ist und das Harz ein kristallines Polypropylen,
Poly(1-buten) oder Poly(4-methyl-1-penten) oder ein zumindest 85 Mol-% davon enthaltendes
Copolymer mit einem a-Olefin mit 2-10 Kohlenstoffatomen ist.
1. Méthode de production d'une composition de résine-caoutchouc partiellement réticulé
par fusion et mélangeage d'un caoutchouc de copolymère d'oléfine durcissable par un
peroxyde et d'une résine de polyoléfine décomposant le peroxyde, avec un composé peroxyde
organique, méthode dans laquelle de caoutchouc et la résine sont mélangés dans un
rapport pondéral dans l'intervalle de 10:90 à 95:5 et sont soumis à un traitement
thermique dynamique en présence de peroxyde, ladite méthode étant caractérisée en
ce que le caoutchouc sous forme de particules et la résine et le peroxyde sont alimentés
dans une extrudeuse à double vis dans laquelle le traitement thermique dynamique est
conduit, dans les conditions suivantes:
où "x" désigne le poids du caoutchouc de copolymère (g/100 particules), et "y" désigne
l'énergie spécifique à l'extrusion (kWh/kg).
2. Méthode selon la revendication 1, caractérisée en ce que les particules de caoutchouc
ont une dimension maximale ne dépassant pas 25 mm.
3. Méthode selon la revendication 2, caractérisée en ce que les particules de caoutchouc
ont une dimension maximale de 0,5 à 20 mm.
4. Méthode selon la revendication 3, caractérisée en ce que x est égal à 1 à 50.
5. Méthode selon la revendication 3 ou 4, caractérisée en ce que y est égal à 1.5
ou moins.
6. Méthode selon l'une quelconque des revendications précédentes, caractérisée en
ce que la résine de polyoléfine est alimentée dans l'extrudeuse sous la forme de particules
ayant un poids dans l'intervalle de 1 à 10 g/100 particules.
7. Méthode selon l'une quelconque des revendications précédentes, caractérisée en
ce que le rapport pondéral caoutchouc:résine est de 20:80 à 90:10.
8. Méthode selon l'une quelconque des revendications précédentes, caractérisée en
ce qu'un adjuvant de réticulation, de préférence le divinylbenzène, est présent durant
le traitement thermique.
9. Méthode selon l'une quelconque des revendications précédentes, -caractérisée en
ce que le caoutchouc est un copolymère amorphe d'oléfine, ou un copolymère amorphe
d'oléfine et de diène non conjugué et la résine est un polypropylène cristallin, un
poly(1-butène) ou un poly(4-méthyl-1-pentène) ou un copolymère contenant au moins
85% molaires de ceci avec une a-oléfine contenant de 2 à 10 atomes de carbone.